Organic solvent and water resistant hydrolytically stable ultraviolet radiation curable coatings for optical fibers

ABSTRACT

Ultraviolet radiation-curable primary coating compositions for optical fibers are disclosed. The primary coatings comprise a polyether polyol-based reactively terminated aliphatic urethane oligomer; one or more diluent monomers terminated with at least one end group capable of reacting with the reactive terminus of the oligomer; an organofunctional silane adhesion promoter; and an optional photoinitiator. Also disclosed are optical fibers coated with the coatings of the invention, and processes for preparing same.

This is a continuation of application Ser. No. 08/169,544 filed Dec. 20,1993, now abandoned, which is in turn a continuation of Ser. No.07/873,105 filed on Apr. 24, 1992, now abandoned.

The present invention relates to radiation-curable primary coatings foroptical fibers, to optical fibers containing such coatings and toprocesses for preparing optical fibers coated with the coatings of theinvention.

Until recently, the optical fiber industry was concentrated on so-called"long haul" applications, wherein optical fibers were used to traverselong distances such as in transoceanic or transcontinental cables. Insuch applications, optical fibers required shielding with voluminousprotective cabling material in sheltered subterranean or submarineenvironments and thus were not directly exposed to environmentalhazards.

A recent trend in the optical fiber market is in local area networks forfiber-to-the-home uses. The fibers in such uses are directly exposed tomuch harsher conditions than previous applications of glass fibers,including severe temperature and humidity extremes. Consequently,previously used coatings do not perform well under such adverseconditions; hence, a need existed for the development of higherperformance coatings. Such coatings needed to be able to withstand theabove conditions, i.e., to possess thermal, oxidative and hydrolyticstability, to be resistant to moisture and to organic solvents and toprotect the fiber over the long term, i.e., over twenty-five years'time.

Optical fibers used for light transmission can be prepared which,immediately after drawing, are exceptionally strong and have very fewintrinsic defects. However, such pristine fibers are very easily flawedby exposure to environmental conditions including dust and moisture.Even a small flaw can reduce the strength of a fiber by an order ofmagnitude, rendering it brittle and easily broken by weak externalforces. Therefore, optical glass fibers have, in the prior art, beenclad with at least one resin coat immediately after their preparation,whose minimum requirement is to protect the underlying pristine fiberfrom such external forces.

Typically, at least two coatings, a primary, or buffer, coating and asecondary coating, have been used. In some cases, however, a monocoat,having properties intermediate to the typical primary and secondarycoatings, is employed. In the case of a dual coat system, the inner, orprimary, coating is applied directly to the glass fiber which, whencured, forms a soft, rubbery, compliant material which serves as abuffer to cushion and protect the fiber by relieving the stressescreated when the fiber is bent, cabled or spooled. Such stress mightotherwise induce microbending of the fibers and cause attenuation of thelight traveling through them, resulting in inefficient signaltransmission. The secondary coating is applied over the primary coating,and must function as a hard, tough protective outer layer, preventingdamage to the glass fiber during processing and use.

Certain characteristics are desirable for the primary coating, andothers for the secondary coating. For example, the primary coating mustmaintain adequate adhesion to the glass fiber during thermal andhydrolyric aging, yet be strippable therefrom for splicing purposes. Itshould resist swelling due to solvent exposure sufficiently to retainits own structural integrity and that of the secondary coating. Themodulus of the primary coating must be low to cushion and protect thefiber by readily relieving the stresses on the fiber which can inducemicrobending and consequent inefficient signal transmission. Thiscushioning effect must be maintained through the temperature range inwhich the fibers may be exposed throughout their lifetime. Thus, it isnecessary for the primary coating to have a low glass transitiontemperature (Tg). This low glass transition temperature will ensure thatthe coating remains in its rubbery state throughout the possible usetemperature range.

The primary coating should also have a relatively high refractive index,i.e., greater than that of the cladding material of the fiber to becoated. This high refractive index allows for a refractive indexdifferential between the glass cladding and the primary coating. Thisdifferential allows errant light signals to be refracted away from theglass core.

Another requisite quality of the primary (buffer) coating is resistanceto moisture. Moisture will rapidly degrade the strength of the coatingitself as well as the underlying glass fibers under stress. The reactionis one of hydrolysis and stress corrosion. Moisture will also adverselyaffect the adhesion of the primary coating to the glass, resulting inpossible delamination. It is therefore desirable for the coating to beas water resistant as possible. Preferably, the primary coating shouldhave a water absorption value of less than 5% by weight, and morepreferably less than 3% by weight.

Yet another desirable property for primary coatings is organic solventresistance. Such solvents can cause the primary coating to swell soseverely as to result in delamination of the coatings from the fiber, orto cause the more rigid secondary coating to crack and fall apart.Solvent exposure can be, in the case of "long haul" optical fibercables, in the form of filling compounds (e.g., mineral oil-based orsilicone-based materials), or, in the case of less protectedfiber-to-the-home applications, various household solvents such as arepresent in cleaners, paints, insect repellents and so forth.Additionally, when such fibers are routed near filling stations,gasoline leakage may result in solvent exposure. Preferably, the coatingshould exhibit an increase in length due to swelling of less than about40%, and more preferably, less than about 35%, after soaking in gasolineat room temperature for four hours, as a measure of organic solventabsorption.

It can be readily appreciated that the attainment of organic solventresistance and water resistance are often at cross purposes, one moreeasily attained with a hydrophilic composition and the other with ahydrophobic composition, and thus difficulty achieved.

Furthermore, the coating should have optimized adhesion to itssubstrate, high enough that it will remain adhered thereto under useconditions, yet not so high as to impair strippability for splicing.

Similarly, the secondary coating must have a number of essential andoptimal qualities. The secondary coating should function as a hardprotective layer which allows the fiber not to be damaged during itsprocessing and use, and thus should have a relatively high glasstransition temperature (Tg) and a high modulus. Furthermore, like theprimary coating, the secondary coating should undergo minimal changes inphysical properties on exposure to organic solvents and moisture.Moreover, secondary coatings should have a low coefficient of friction(COF) to facilitate winding and unwinding of the fibers on spools and toallow the fibers to slide easily along each other in a cable structure,thus relieving stress, but not so low as to result in a reduced tendencyto stay aligned on the spool.

Again, in monocoat applications, the single coating layer shouldoptimally have certain properties intermediate those typically seen inprimary and secondary coatings, i.e., with respect to modulus, Tg andrefractive index.

Still other properties exist which are desirable in both primary andsecondary coatings. For example, fiber manufacturers are motivated tocoat the fibers as rapidly as possible to attain the economy of fastercure speeds, as these result in higher line speeds. The cure speeds ofcoating materials may be determined by constructing a UV dose versusmodulus curve. The lowest UV dose at which the coating modulus exhibitsdose independence is considered its cure speed. There is therefore ademand for faster curing coatings; for example, high line speeds areobtained with primary and secondary coatings which may be appliedwet-on-wet and simultaneously ultraviolet light-cured. One way of doingthis is described in U.S. Pat. No. 4,474,830, issued Oct. 2, 1984 toCarl R. Taylor, which patent is expressly incorporated herein byreference.

Another desirable objective for both primary and secondary UV-curablecoatings is to minimize the amount of unbound material in the coatingafter cure. Even when the cured coatings are considered 100% solids,there may still exist a small amount of material which does notchemically bind into the polymer network on curing. Examples of suchmaterials in the cured coatings include unreacted monomer, unreactedphotoinitiator, certain non-functional additives and so forth. Thepresence of excessive amounts of such materials is undesirable, inasmuchas volatilization of such components over time may change the physicalproperties of the coating. For example, volatile materials from theprimary coating may permeate into the secondary coating, tending toplasticize it and resulting in strength loss. Also, volatile materialsmay cause production of unpleasant odors.

Still other important qualities of both optical fiber coatings areviscosity and shelf life. Good shelf life is considered formulationstability of at least six to twelve months. Viscosity can typically besomewhat adjusted by regulation of the temperature at which the coatingsare applied. However, it is advantageous to set the viscosity highenough so as to maintain proper theology and handling of the coating onapplication, but low enough to facilitate bubble release and to minimizethe amount of heat needed in the preparation. Excessive heating isundesirable inasmuch as it may result in premature gelling or viscositybuildup due to possible thermal initiation of polymerization.

PRIOR ART COATINGS

Various single or double layer fiber coatings exist in the prior art.Among these are epoxy- or urethane-based resins. However, many of theseresins cure slowly; have poor moisture or organic solvent resistance orpoor hydrolytic, thermal and oxidative stability; and have undesirableyellowing properties.

There have also been developed primary (buffer) coatings which cure onexposure to ultraviolet radiation. Such prior art primary coatings,however, have conventionally not been very moisture resistant and havesome of the same deficiencies as above. In general, coatings formulatedfor moisture resistance are not resistant to organic solvents, and viceversa.

To obviate these flaws, the primary-coated optical fibers of the priorart have been topcoated with a tough and flexible overcoat whichpossesses superior resistance to moisture and abrasion. Prior artcoatings have included extruded nylon "jacket" coatings, which are,however, more expensive and more difficult to apply than would be anultraviolet-cured coating.

There have recently been developed optical fiber coats which are verymoisture resistant and which have excellent thermal, hydrolytic andoxidative stability. Applicant's U.S. Ser. No. 742,531, filed Aug. 8,1991, (a continuation application of Ser. No. 350,239, filed May 11,1989), now U.S. Pat. No. 5,146,531 teaches coating compositions preparedfrom acrylate or methacrylate based components, e.g., a primary coatingincluding, inter alia, an acrylated urethane oligomer based on ahydrocarbon polyol; an alkyl acrylate monomer; and a photoinitiator, anda secondary coating including a polyester and/or polyether basedacrylated urethane oligomer; an acrylated compound capable of adjustingviscosity; and a photoinitiator.

Applicant's U.S. Ser. No. 868,933, filed Apr. 16, 1992 (acontinuation-in-part of the aforedescribed application), now U.S. Pat.No. 5,352,712, teaches that compositions analogous to those taught inits parent, but bearing any reactive end groups which do not adverselyeffect the cured coatings prepared from them, may be used. Each of theseapplications are expressly incorporated by reference herein.

While each of these compositions is suitably water resistant for mostoptical fiber coating uses, they are so hydrophobic as to not beresistant to some organic solvents to which the fiber may be exposed.

Therefore, the present invention seeks to provide a primary coatingwhich, when cured, has maximal thermal, oxidative and hydrolyticstability, wherein the primary coating is adequately adherent to theglass fiber yet strippable therefrom; provides adequate cushioning ofthe fiber; has a relatively low glass transition temperature; and iscapable of relieving stress upon the fiber. It should also be resistantto swelling by resisting solvent absorption and be moisture resistant aswell.

SUMMARY OF THE INVENTION

It has now been discovered that a composition which, when cured, hasexcellent resistance to moisture and to organic solvents and concomitantswelling, as well as having excellent thermal, oxidative and hydrolyticstability, can be made.

Accordingly, the radiation-curable primary coating for an optical fiberof the present invention comprises, in one embodiment:

(A) from about 10 percent to about 90 percent by weight of a reactivelyterminated urethane oligomer which is the reaction product of (i) apolyether polyol; (ii) an aliphatic polyisocyanate; and (iii) anendcapping monomer capable of providing a reactive terminus;

(B) from about 5 percent to about 80 percent by weight of one or moremonomer diluents which are terminated with at least one end groupcapable of reacting with the reactive terminus of (A);

(C) from about 0.1 percent to about 3.0 percent by weight of anorganofunctional silane adhesion promoter; and

(D) optionally, from about 1.0 percent to about 10.0 percent by weightof a photoinitiator,

wherein all of the stated percentages are percentages by weight based ontotal weight of (A), (B), (C) and (D) and, preferably, wherein thecomposition, after radiation cure, exhibits an increase in length fromswelling of no more than about 40 percent when soaked in gasoline atroom temperature for four hours and a water absorption value, as definedherein, of no more than about 5% by weight.

Preferably, the reactive termini of (A) and (B) are acrylate ormethacrylate.

The primary coating may optimally contain other materials, such as achain transfer agent, preferably a mercapto-functional chain transferagent, and one or more stabilizers.

A coated optical fiber has also been developed. In one embodiment, theoptical fiber comprises an optical fiber coated with the primary coatinglayer as described above, and, in another, an optical fiber coated withprimary and secondary coating layers.

A process for preparing a coated optical fiber has also been developed.In one embodiment, the process comprises applying to an optical fiber aprimary coating layer as described above and radiation-curing thecoating. In another embodiment, both a primary and a secondary coatinglayer are applied and radiation cured.

The coating compositions of the invention are also useful for othercoating and protective purposes. They can be formulated to be useful onglass, ceramic, granite, and marble surfaces, and the like.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention relates in part to radiation-curable primary coatings foroptical fibers. The optical fibers which are coated may comprise a glasscore and a glass cladding layer. The core, for example, may comprisesilica doped with oxides of germanium or phosphorus and the cladding, apure or doped silicate such as fluorosilicate. Alternately, the fibersmay comprise a polymer-clad silica glass core. Examples of such polymercladdings include organosiloxanes such as polydimethylsiloxane or afluorinated acrylic polymer.

The primary coating, when cured, should have, inter alia, the followingproperties: moisture resistance; organic solvent resistance; ease ofapplication; acceptable adhesion without compromising strippability; lowvolatiles content; low tensile modulus over the life of the fiber; lowglass transition temperature; and long shelf life. Furthermore, itshould be transparent; nonmalodorous; fast curing; and remain adherent,even upon aging in high heat and humidity environments. Additionally,the cured primary coating should maintain its excellent properties underaccelerated aging conditions of increased temperature and humidity as ameasure of its long term thermal, hydrolytic and oxidative stability.

The present invention involves the recognition that it is possible,through the judicious choice of ingredients and proportions, toformulate a primary coating composition meeting these criteria.

The primary coating composition of the present invention contains fourbasic ingredients, (A), (B), (C) and (D).

(A.) The Polyether Polyol-Based Oligomer

The first ingredient is a reactively terminated polyether polyol-basedurethane oligomer (A). This component comprises from about 10 percent toabout 90 percent by weight of the composition base on the total weightof the (A), (B), (C) and (D) ingredients of the composition. Preferably,this oligomer comprises from about 20 percent to about 80 percent, andmore preferably from about 30 percent to about 70 percent by weight ofthe composition, based on the total weight of the (A) through (D)ingredients.

The particular oligomer used in the present invention is chosen toimpart good thermal, oxidative and hydrolytic stability to the system,as well as to confer both moisture and organic solvent resistance.

It has been known in the art that various types of UV-curable oligomersexist which may yield a soft, compliant, low glass transitiontemperature-type coating. Acrylate-or methacrylate-terminated monomersare particularly commonly used due to their ease of cure uponultraviolet radiation. One system known in the art is acrylate-endcappedpolybutadiene-type rubber or rubber-modified acrylated monomers as baseresins. While these systems have excellent low temperature propertiesand are hydrophobic for moisture resistance, their internalcarbon-carbon double bonds (unsaturation) make them susceptible tooxidation over a long period of time.

It is also known in the art to employ acrylated silicones as base resinsin such compositions. While these have good low temperature propertiesand hydrophobicity, they are difficult to formulate with a suitably highrefractive index; tend to have poor thermal stability; and may besusceptible to hydrogen outgassing which can lead to signal attenuationin fibers so coated.

Yet another system known in the art involves the use of acrylatedfluorocarbons. While these are hydrophobic and thermally stable, theyare typically incompatible with most non-halogenated organic compounds.Additionally, they are very expensive relative to other systems.

To overcome many of the disadvantages of the prior art systems, it maybe tried to utilize a urethane system based on one of a variety ofbackbones. In general, urethane acrylate systems based on polyethers orpolyesters were usually characterized by poor water resistance and bythermal instability. Additionally, known urethane oligomers based onaromatic isocyanates displayed thermal instability and tended to yellow.While polyether-based urethane acrylates have excellent low Tgproperties, when used alone, many are not hydrophobic enough for opticalfiber applications and are susceptible to oxidation. Polyester-basedurethane acrylates, on the other hand, have good thermal stability butare susceptible to hydrolysis.

Thus, the present invention uses an oligomer which, in combination withthe other components of this invention, obviates many of the aboveproblems.

The oligomer (A) utilized in the present invention is the reactionproduct of (i) a polyether polyol; (ii) an aliphatic polyisocyanate; and(iii) an endcapping monomer capable of supplying a reactive terminus.

The oligomeric component may contain very small amounts of urethaneacrylates based on polyesters, but preferably contains onlypolyether-based oligomers, for optimal long term stability.

The polyether polyol is based on a straight chained or branched alkyleneoxide of from one to about twelve carbon atoms. The polyether polyol maybe prepared by any method known in the art.

The polyisocyanate component (ii) is non-aromatic. Oligomers based onaromatic polyisocyanates effect yellowing in the cured coating.Non-aromatic polyisocyanates of from 4 to 20 carbon atoms may beemployed. Suitable saturated aliphatic polyisocyanates include but arenot limited to isophorone diisocyanate;dicyclohexylmethane-4,4'-diisocyanate; 1,4-tetramethylene diisocyanate;1,5-pentamethylene diisocyanate; 1,6-hexamethylene diisocyanate;1,7-heptamethylene diisocyanate; 1,8-octamethylene diisocyanate;1,9-nonamethylene diisocyanate; 1,10-decamethylene diisocyanate;2,2,4-trimethyl- 1,5-pentamethylene diisocyanate; 2,2'-dimethyl-1,5-pentamethylene diisocyanate; 3-methoxy-1,6-hexa-methylene diisocyanate;3-butoxy-1,6-hexamethylene diisocyanate; omega, omega'-dipropyletherdiisocyanate; 1,4-cyclohexyl diisocyanate; 1,3-cyclohexyl diisocyanate;trimethylhexamethylene diisocyanate; and mixtures thereof. Small amountsof aromatic polyisocyanates may be used; however, long term stability onaging may suffer somewhat.

The reaction rate between the hydroxyl-terminated polyol and thediisocyanate may be increased by use of a catalyst in the amount of 100to 200 ppm. Suitable catalysts include but are not limited to dibutyltin dilaurate, dibutyl tin oxide, dibutyl tin di-2-hexoate, stannousoleate, stannous octoate, lead octoate, ferrous acetoacetate, and aminessuch as triethylamine, diethylmethylamine, triethylenediaminedimethylethylamine, morpholine, N-ethyl morpholine, piperazine,N,N-dimethyl benzylamine, N,N-dimethyl laurylamine, and mixturesthereof.

The endcapping monomer (iii) may be one which is capable of providing atleast one reactive terminus and which preferably provides acrylate ormethacrylate termini. Suitable hydroxyl-terminated compounds which maybe used as the endcapping monomers include but are not limited tohydroxyalkyl acrylates or methacrylates such as hydroxyethyl acrylate,hydroxyethyl methacrylate, hydrozypropyl acrylate hydroxypropylmethacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, and soforth.

A particularly preferred endcapping monomer is hydroxyethyl acrylate orhydroxyethyl methacrylate.

The molar ratio of the polyol, diisocyanate and endcapping monomer ispreferably approximately 1:2:2.

Some commercially available oligomers which are suitable for the (A)component of this invention include but are not limited to thefollowing:

(1.) Echo Resins ALU-350 series resins, i.e., 350, 351, 352 and 353,from Echo Resins and Laboratory, Versailles, Mo., all polytetramethylenepolyol-based acrylated aliphatic urethane oligomers of increasingmolecular weight and viscosity and decreasing modulus with increasingnumber in the series. Certain physical properties for this series ofresins are summarized below:

    ______________________________________                                                 ALU-350 ALU-351   ALU-352  ALU-353                                   ______________________________________                                        Density @ 20° C.                                                       (g/cm.sup.3)                                                                             1.052     1.048     1.027  1.019                                   (lbs/gal)  8.76      8.73      8.55   8.49                                    Refractive Index                                                                         1.496     1.492     1.478  1.468                                   Viscosity                                                                     @ 78° F. (cps)                                                                    320,000   120,000   wax    wax                                     @ 140° F. (cps)                                                                   7,300     5,400     8,900  21,750                                  Color, Gardner                                                                           <1        <1        <1     <1                                      Functionality                                                                            2         2         2      2                                       Percent    3.6       2.8       1.7    1.3                                     Shrinkage, Cured                                                              Relative   1.0       1.3       2.0    2.7                                     Molecular Weight                                                              ______________________________________                                    

In general, the lower molecular weight members of the series arepreferred because they appear to cause less solvent swelling in curedcoatings including them.

The methacrylate equivalents of these oligomers are equally suitable.

(2) Purelast® aliphatic urethane acrylate oligomers based on polyetherbackbones, available from Polymer Systems Corporation, Orlando, Fla.Suitable Purelast® oligomers include 566, 566A, 569, 569A, 586, 586A,590, 590A, 595, 595A, 597A and 598A. This series of oligomers increasesin modulus with increasing number in the series. These oligomers areeither difunctional (no suffix) or monofunctional ("A" suffix). All ofthese oligomers are sold neat, except for 597A and 598A, which include7% and 10% isobornyl acrylate, respectively.

Methacrylate anologs of these oligomers are suitable as well.

(3) Ebecryl® 8800, Ebecryl® 270, and Ebecryl® 4826 oligomers, all fromRadcure Specialties Inc., Louisville, Ky., all aliphatic urethanediacrylate oligomers based on polyethers.

Ebecryl® 8800 oligomer is diluted 10% with ethoxyethoxyethyl acrylate;has a viscosity at 65° C. of 8000-18,000 cps and a Gardner Color Indexof 2 max. Its density is 8.75 pounds per gallon; its theoreticalfunctionality is 2.5 and its theoretical molecular weight is 1700. Whencured it has a tensile strength of 3150 psi; a tensile elongation of83%, and a glass transition temperature of 48° C.

Ebecryl® 270 oligomer, previously sold as Ebecryl® 4826 oligomer,contains no diluent monomer; has a viscosity of 2500-3500 cps at 60° C.and a Gardner Color Index of 2 max. Its density is 8.91 pounds pergallon; its theoretical functionality is 2 and its theoretical molecularweight is 1500. When cured it has a tensile strength of 1200 psi; atensile elongation of 87% and a glass transition temperature of -27° C.

Methacrylate equivalents of these oligomers may also be used.

(4) Uvithane® ZL-1178 oligomer from Morton Thiokol, Inc., MortonChemical Division, Princeton, N.J., polyether based aliphatic urethaneacrylate. This oligomer has a viscosity of 55-75 poises at 120° F. and700-800 poises at 78° F. and, when cured neat, has a tensile strength of325 psi and an ultimate elongation of 45%.

The methacrylate analog of this monomer may be used as well.

(5) Furthermore, any polyether-based aliphatic urethane acrylate ormethacrylate oligomer of the type exemplified above is believed to besuitable so long as the desirable properties of the claimed compositionare not adversely effected.

The primary coating containing the oligomer of this invention has awater absorption value of less than about 5% by weight, and preferablyless than about 3%. Furthermore, the coating should swell less than 40%in length, and preferably less than about 35% in length, when soaked ingasoline for about 4 hours at room temperature.

(B.) The Diluent Monomer

The second essential component of the composition is a diluent monomerwhich is terminated with at least one end group capable of reacting withthe reactive terminus of (A). Again, this terminus is preferablyacrylate or methacrylate.

The monomer is selected to be one that will adjust the total primarycoating composition to a viscosity in the range of about 1,000 cps(centipoises) to about 10,000 cps, and preferably in the range of about4,000 cps to about 8,000 cps, measured by a Brookfield viscometer, modelLVT, spindle speed of 6 rpm, spindle #34, at 25° C. Additionally, it ischosen to be soft-curing and to have a low Tg, thus lowering the Tg ofthe composition. Furthermore, a specific diluent may be chosen which iscapable of adjusting the refractive index of the whole composition, aswill be further discussed below.

The monomer (B) comprises from about 5 percent to about 80 percent byweight of the composition, based on the total weight of (A), (B), (C)and (D). Preferably, it comprises from about 10 percent to about 70percent, and more preferably from about 10 percent to about 60 percentby weight of the composition, based upon the total weight of (A), (B),(C) and (D).

This diluent monomer may be either straight chained or branched, andshould preferably be at least partially aliphatic. One type of diluentwhich may be used is an alkyl acrylate or methacrylate having about 6 to18 carbon atoms in the alkyl moiety of the molecule.

Suitable examples of such monomers include but are not limited toacrylates land methacrylates such as hexyl acrylate; hexyl methacrylate;2-ethylhexyl acrylate; 2-ethylhexyl methacrylate; isooctyl acrylate;isooctyl methacrylate; octyl acrylate; octyl methacrylate; decylacrylate; decyl methacrylate; isodecyl acrylate; isodecyl methacrylate;lauryl acrylate; lauryl methacrylate; tridecyl acrylate; tridecylmethacrylate; palmitic acrylate; palmitic methacrylate; stearylacrylate; stearyl methacrylate; C₁₄ -C₁₅ hydrocarbon diol diacrylates;C₁₄ -C₁₅ hydrocarbon diol dimethacrylates; and mixtures of the above.

Preferred alkyl acrylate monomers include stearyl acrylate, laurylacrylate and isodecyl acrylate. A particularly preferred one is laurylacrylate.

As mentioned above, the diluent monomer may also be one which is capableof adjusting the refractive index of the composition. Such monomers,when used, may, for example, contain (1) an aromatic moiety; (2) amoiety providing a reactive (e.g., acrylic or methacrylic) group; and(3) a hydrocarbon moiety.

The aromatic moiety of such refractive index modifying monomer (B) isitself capable of raising the refractive index; however, the hydrocarbonmoiety may, assist in increasing the compatibility of this monomer withthe oligomer (A). The moiety providing a reactive group (e.g., anacrylate or methacrylate group) renders the compound compatible with thesystem as a whole, inasmuch as it has available reactive terminationwhich allows it to crosslink with the rest of the composition uponultraviolet curing, thus minimizing the volatiles content of the curedsystem. Samples of aromatic monomers additionally containing hydrocarboncharacter and a vinyl group include but are not limited to polyalkyleneglycol nonylphenylether acrylates such as polyethylene glycolnonylphenylether acrylate or polypropylene glycol nonylphenyletheracrylate; polyalkylene glycol nonylphenylether methacrylates such aspolyethylene glycol nonylphenylether methacrylate or polypropyleneglycol nonylphenylether methacrylate; and mixtures of these.

In each case, the phenyl group serves to increase the refractive indexof the coating and the nonyl component renders the composition somewhatmore compatible with the aliphatic oligomer (A). This monomer is capableof increasing the refractive index of the composition relative to thatof a composition comprising only (A), (C) and (D). A suitable primarycoating composition may, for example, have a refractive index of greaterthan or equal to about 1.48.

The refractive index of the primary coating must be higher than that ofthe cladding of the fiber. If the fibers coated with the coatingcomposition of the present invention are down-doped, i.e., containdopants which lower the refractive index of the fiber itself, therefractive index of the coating will be different enough from that ofthe fiber so that errant signals will be refracted away even without theincorporation of this component. Therefore, in such embodiments, arefractive index modifying monomer is not essential to the compositionand other diluents may instead be used.

Further, the diluent monomer may be any of those known in the art, whichdo not adversely affect the composition. In a preferred embodiment, thediluent monomer component (B) comprises a mixture of oligomers, e.g., asmall portion of a monomer capable of adjusting the refractive index andthe balance of an alkyl acrylate or methacrylate which is whollyaliphatic, optimizing compatibility and stability.

(C.) The Adhesion Promoter

The third ingredient is an organofuntional silane adhesion promoter (C).Adhesion becomes a particularly pertinent problem in high humidity andhigh temperature environments, where delamination is more of a risk. Invery protected environments, this component may be optional, such as inconditions of low humidity (i.e., below 50% relative humidity) and lowtemperature (i.e., below 25° C.).

It is known in the art to use either acid-functional materials ororganofunctional silanes to promote adhesion of resins to glass. Whileacid-functional materials are operative herein, organo-functionalsilanes are preferred. Acid-functional materials are less preferredbecause of their possible corrosivity towards the materials, and theirtendency to lose their adhesion properties on exposure to moisture.Silanes tend to be much more suitable in terms of these factors and,therefore, are the adhesion promoters of choice. Additionally, it isuseful to have an adhesion promoter having a functionality which bindsin with the system during cure, to maximize its adhesion promotion aswell as to minimize the quantities of unbound volatiles.

Various suitable organofunctional silanes include but are not limited toamino-functional silanes; acrylamido functional silanes;allyl-functional silanes; vinyl-functional silanes; acrylate-functionalsilanes; methacrylate-functional silanes; and mercapto-functionalsilanes. The adhesion promoters preferably are methoxy-orethoxy-substituted as well.

Preferred organofunctional silanes include but are not limited tomercaptoalkyl trialkoxy silane, methacryloxyalkyl trialkoxy silanes,aminoalkyl trialkoxy silane, vinyl alkoxy silane, mixtures thereof, andthe like. Methacrylated silanes are desirable, inasmuch as they bind inwell with the cured system, but tend to slow down the cure speed of thesystem. The mercaptofunctional adhesion promoters also chemically bindin during cure, but do not appreciably slow down the cure speed of thesystem. Allyl-functional and vinyl-functional silanes are also desirablewhen they are chosen to bind in well with the system used.

Some preferred organofunctional silanes that enhance adhesion in humidconditions include but are not limited to vinyl-tris-(2-methoxyethoxysilane), 3-aminopropyl triethoxy silane, 3-methacryloxypropyl-trimethoxysilane, 3-mercaptopropyl trimethoxy silane,3-mercaptopropyl(gamma-mercaptopropyl)triethoxy silane, vinyl triacetoxysilane, beta-(3,4-epoxycyclohexyl) ethyl trimethoxy silane,gamma-glycidoxypropyl trimethoxy silane, 3-vinylthiopropyl trimethoxysilane, and mixtures thereof. A particularly preferred adhesion promoteris vinyl-tris-(2-methoxyethoxy silane).

The silane component, when used, should be incorporated into thecomposition in a small but effective amount to enhance the adhesion ofthe composition to the surface of an inorganic substrate, which, in thepreferred embodiment, is glass fiber, and in other embodiments, may beglass, enamel, marble, granite or the like. The silane component, whenused, comprises from about 0.1 percent to about 3.0 percent by weight ofthe composition, based on total weight of the ingredients (A), (B) (C)and (D). Preferably, the silane comprises from about 0.2 percent toabout 2.0 percent, and more preferably from about 0.3 percent to about1.0 percent, based on the total weight of the oligomer, diluent monomer,silane and photoinitiator.

(D.) The Photoinitiator

A fourth ingredient of the primary coating composition is an optionalphotoinitiator (D). This ingredient is only required in embodimentswherein the coating is to be ultraviolet radiation-cured; in otherembodiments, such as wherein electron beam cure is envisioned, thephotoinitiator may be omitted. The photoinitiator, when used in a smallbut effective amount to promote radiation cure, must provide reasonablecure speed without causing premature gelation of the composition.Further, it must not interfere with the optical clarity of the curedoptical coating. Still further, the photoinitiator must itself bethermally stable, and non-yellowing and efficient.

Suitable photoinitiators include but are not limited to the following:hydroxycyclohexylphenyl ketone; hydroxymethylphenyl propanone;dimethoxyphenylacetophenone; 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propanone-1;1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one;1-(4-dodecylphenyl)-2-hydroxy-2-methylpropan-1-one;4-(2-hydroxyethyoxy)phenyl-2(2-hydroxy-2-propyl)ketone; diethoxyphenylacetophenone; and mixtures of these.

The photoinitiator preferably comprises from about 1.0 percent to about10.0 percent by weight of the composition, based upon the totalcomposition of the (A) through (D) ingredients. Preferably, the amountof photoinitiator is from about 1.5 percent to about 8.0 percent, andmore preferably from about 2.0 percent to about 7.0 percent by weight,based upon total weight of (A), (B), (C) and (D) ingredients.

A particularly preferred photoinitiator is hydroxycyclohexylphenylketone. The photoinitiator should be chosen such that a cure speed, asmeasured in a dose versus modulus curve, of less than 1.0 J/cm², andpreferably less than 0.5 J/cm², is required, when the photoinitiator isused in the designated amount.

Other Optional Components

Various optional components may be used in the primary coating beyondthe (A) through (D) components which are described above. For example,optional chain transfer agents (E) may be used to control the modulusand glass transition temperature of the coating. One way known in theart to control the molecular weight and, consequently, the modulus andglass transition temperature of a polymerization product is to use oneor more chain transfer agents. The addition of a chain transfer agent toa formulation lowers the molecular weight of a polymer produced andresults in a lower modulus, lower glass transition temperature coating.

Preferred chain transfer agents are mercapto compounds, optionallyhaving a hydrocarbon chain of at least eight carbon atoms. Examples ofsuitable mercapto chain transfer agents include but are not limited tomethyl thioglycolate; methyl-3-mercaptopropionate; ethyl thioglycolate;butyl thioglycolate; butyl-3-mercaptopropionate; isooctyl thioglycolate;isooctyl-3-mercaptopropionate; isodecyl thioglycolate; isodecyl-3-mercaptopropionate; dodecyl thioglycolate; dodecyl-3-mercaptopropionate;octadecyl thioglycolate; and octadecyl-3-mercaptopropionate.Parathiocresol; thioglycolic acid; and 3-mercaptopropionic acid may alsobe used, but may display some incompatibility with the resin and mayproduce odor problems. In general, lower molecular weight chain transferagents are preferred.

A particularly preferred chain transfer agent isisooctyl-3-mercaptopropionate (IOMP).

The chain transfer agent may, if used, comprise from about 0.1 percentto about 10.0 percent by weight of the composition based upon the totalweight of ingredients (A) through (D). Preferably, the chain transferagent comprises from about 0.25 percent to about 9.0 percent by weight,and still more preferably from about 0.5 percent to about 8.0 percent byweight, based on the total weight of the (A), (B), (C) and (D)components.

To improve shelf life (storage stability) of the uncured coating, aswell as to increase thermal and oxidative stability of the curedcoating, one or more stabilizers (F) may be included in the composition.Examples of suitable stabilizers include tertiary amines such asdiethylethanolamine, diethyl hydroxyl amine and trihexylamine; hinderedamines; organic phosphites; hindered phenols; mixtures thereof; and thelike. Some particular examples of antioxidants which can be used, aloneor in combination, include but are not limited tooctadecyl-3(3',5'-di-tert-butyl-4'-hydroxyphenyl) propionate;thiodiethylene bis (3,5-di-tert-butyl-4-hydroxy) hydrocinnamate;butylated paracresol-dicyclopentadiene copolymer and tetrakis [methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane. Additionally,certain silanes in small quantities, e.g., as low as 0.0001 percent to0.01 percent by weight, may be used as stabilizers. An example of asuitable silane is 3-aminopropyl trimethoxysilane.

When a stabilizer is used, it may be incorporated in a total amount offrom about 0.0001 percent to about 3.0 percent, based on the weight ofthe (A) through (D) ingredients. Preferably, it is included in the rangefrom about 0.25 percent to about 2.0 percent by weight, and morepreferably in the range from about 0.5 percent to about 1.5 percent byweight, based on the total weight of the (A) through (D) ingredients.Desirable properties of a stabilizer include (1) non-migration (probablyenhanced by low polarity and high molecular weight) and (2) basicity (toallow it to help in neutralizing residual acid which might prematurelyinitiate polymerization). Preferred stabilizers include thiodiethylenebis (3,5-di-tert-butyl-4-hydroxy) hydrocinnamate and 3-aminopropyltrimethoxysilane.

PREFERRED COMPOSITIONS

Preferred primary compositions for coating an optical fiber, then,comprise the following:

(A) from about 30 percent to about 70 percent by weight of an aliphaticurethane acrylate oligomer having as a backbone polytetramethylenepolyol;

(B) from about 10 percent to about 60 percent by weight of polypropyleneglycol nonylphenylether acrylate;

(C) from about 0.3 percent to about 1.0 percent by weight ofvinyl-tris-(2-methoxyethoxy silane) adhesion promoter;

(D) from about 2.0 percent to about 7.0 percent by weight ofhydroxycyclohexylphenyl ketone photoinitiator;

(E) from about 0.5 percent to about 8.0 percent by weight ofisooctyl-3-mercaptopropionate, a chain transfer agent;

(F) from about 0.5 percent to about 1.5 percent of thiodiethylenebis-(3,5-di-tert-butyl-4-hydroxy) hydrocinnamate stabilizer; and

(G) from about 0.0001 to about 0.01 percent by weight of 3-aminopropyltrimethoxy silane stabilizer,

wherein all of the stated percentages are percentages by weight, basedupon total weight of (A) through (D), inclusive,

and wherein the composition, after radiation cure, exhibits an increasein length from swelling of no more than about 40 percent when soaked ingasoline at room temperature for four hours and a water absorptionvalue, as described in Example I, below, of no more than about 5% byweight.

Two other preferred primary coatings are ones wherein the (B) component,above, comprises either a mixture of polyethylene glycolnonylphenylether acrylate with lauryl acrylate or polyethylene glycolnonylphenylether acrylate alone.

The primary coating of this invention may either be topcoated with asecondary coating as known in the art, or may, in some cases, iftailored to be suitable therefor, be a monocoat wherein only thisprimary coating is required. A suitable secondary optical fiber coating,when used, optimally possesses good thermal, oxidative and hydrolyticstability; hardness; high modulus; high glass transition temperature;and high refractive index.

An optional secondary coating may be applied atop the primary coatingsof the invention. Suitable secondary coatings are those which are knownin the art, including but not limited to those disclosed in copendingapplication U.S. Ser. No. 868,933, filed Apr. 16, 1992, now U.S. Pat.No. 5,352,712, (incorporated herein by reference).

Such secondary coating may, for example, comprise from about 10 percentto about 90 percent by weight of an aliphatic urethane oligomer based ona polyester and/or polyether and containing a reactive terminus; fromabout 20 percent to about 60 percent by weight of a hydrocarbonaceousviscosity-adjusting component capable of reacting with the reactiveterminus of the oligomer; and optionally, from about 0.05 percent toabout 10.0 percent by weight of a photoinitiator.

One preferred secondary coating may comprise from about 40 percent toabout 80 percent by weight of a mixture of aliphatic urethane acrylateoligomers based on polyether backbones; from about 25 percent to about50 percent by weight of a mixture of isobornyl acrylate and hexanedioldiacrylate; and from about 2.0 percent to about 7.0 percent by weight ofhydroxycyclohexylphenyl ketone photoinitiator.

PREPARATION OF A COATED OPTICAL FIBER

The invention also relates to a process for preparing a coated opticalfiber. The process comprises

(1) applying to an optical glass fiber a primary coating compositionlayer comprising

(A) from about 10 percent to about 90 percent by weight, based upontotal weight of (A), (B), (C) and (D), of a reactively terminatedurethane oligomer which is the reaction product of (i) a polyetherpolyol; (ii) an aliphatic polyisocyanate; and (iii) an endcappingmonomer capable of supplying a reactive terminus;

(B) from about 5 percent to about 80 percent by weight, based upon totalweight of (A), (B), (C) and (D), of one or more monomer diluentsterminated with at least one end group capable of reacting with thereactive terminus of (A);

(C) from about 0.1 percent to about 3.0 percent by weight of anorganofunctional silane adhesion promoter; and

(D) optionally, from about 1.0 percent to about 10.0 percent by weight,based upon total weight of (A), (B), (C) and (D), of a photoinitiator,

wherein the composition, after radiation cure, exhibits an increase inlength from swelling of no more than about 40 percent when soaked ingasoline at room temperature for four hours and a water absorption valueof no more than about 5% by weight; and

(2) radiation-curing said coating in situ.

The reactive termini of (A) and (B) are preferably selected fromacrylate and methacrylate.

In one embodiment, the process comprises applying only the primarycoating of the invention to the optical fiber and radiation-curing thecoating in situ.

In an alternative embodiment, a secondary coating may be applied atopthe primary coating of this invention, and the two coatingssimultaneously radiation cured.

The primary and/or secondary coatings may be applied and cured by anymethod known in the art. A preferred method, whereby two coatings areapplied wet-on-wet, is disclosed in U.S. Pat. No. 4,474,830 to C. Taylorof AT&T Bell Laboratories. The coating or coatings may then be cured insitu, preferably by ultraviolet irradiation, to obtain a cured polymericcoating. Alternatively, the primary coating may be applied and cured,after which the secondary coating may be applied and cured.

COATED OPTICAL FIBERS OF THE INVENTION

The invention further relates to optical fibers, and especially to glassoptical fibers, that are coated with the primary coating of thisinvention alone, or coated with the primary coating of this inventionand a secondary coating.

In one embodiment, the invention is a coated optical fiber comprising:

(a) a glass optical fiber;

(b) a radiation cured primary coating layer comprising the curedreaction product of:

(A) from about 10 percent to about 90 percent by weight of a reactivelyterminated urethane oligomer which is the reaction product of (i) apolymer polyol, (ii) an aliphatic polyisocyanate, and (iii) anendcapping monomer capable of supplying a reactive terminus;

(B) from about 5 percent to about 80 percent by weight of one or moremonomer diluents which are terminated with at least one end groupcapable of reacting with the reactive terminus of (A);

(C) from about 0.1 to about 3.0 percent by weight of an organofunctionalsilane adhesion promoter; and

(D) optionally, from about 1.0 percent to about 10.0 percent by weightof a photoinitiator,

wherein all of the stated percentages are precentages by weight based ontotal weight of (A), (B), (C) and (D); and

(c) a radiation cured secondary coating layer comprising the curedreaction product of

(I) from about 10 percent to about 90 percent by weight of an aliphaticurethane oligomer based on a polyester and/or polyether and containing areactive terminus;

(II) from about 20 percent to about 60 percent by weight ofhydrocarbonaceous viscosity-adjusting component capable of reacting withthe reactive terminus of (I);

(III) optionally, from about 0.05 percent to about 10.0 percent byweight of a photoinitiator, wherein all of the stated percentages arepercentages by weight based on total weight of (I), (II) and (III).

In a preferred embodiment, the invention is a coated optical fibercomprising:

(a) a glass optical fiber;

(b) a radiation-cured primary coating layer comprising the curedreaction product of

(A) from about 10 percent to about 90 percent by weight of an acrylatedor methacrylated urethane oligomer which is the reaction product of (i)a polyether polyol; (ii) an aliphatic polyisocyanate; and (iii) anendcapping monomer selected from the group consisting ofhydroxyalkylacrylate and hydroxyalkylmethacrylate;

(B) from about 5 percent to about 80 percent by weight of one or moreacrylate or methacrylate monomer diluents;

(C) from about 0.1 percent to about 3.0 percent by weight of anorganofunctional silane adhesion promoter; and

(D) optionally, from about 1.0 percent to about 10 percent by weight ofa photoinitiator,

wherein all of the stated percentages are percentages by weight based ontotal weight of (A), (B), (C) and (D); and

(c) a radiation-cured secondary coating layer comprising the curedreaction product of

(I) from about 40 percent to about 80 percent by weight of a mixture ofaliphatic urethane acrylate oligomers based on polyether backbones;

(II) from about 25 percent to about 50 percent by weight of a mixture ofisobornyl acrylate and hexanediol diacrylate; and

(III) from about 2.0 percent to about 7.0 percent by weight ofhydroxycyclohexylphenyl ketone photoinitiator; and

wherein all of the stated percentages are percentages by weight based onthe total weight of (I), (II) and (III).

In another preferred embodiment, the invention is a coated optical fibercomprising

(a) a glass optical fiber;

(b) a radiation-cured primary coating layer comprising the curedreaction product of

(A) from about 30 percent to about 70 percent by weight of an aliphaticurethane acrylate oligomer having as a backbone a tetramethylene polyol;

(B) from about 10 percent to about 60 percent by weight of polypropyleneglycol nonylphenylether acrylate;

(C) from about 0.3 percent to about 1.0 percent by weight ofvinyl-tris-(2-methoxyethoxy silane) adhesion promoter; and

(D) from about 2.0 percent to about 7.0 percent by weight ofhydroxycyclohexylphenyl ketone photoinitiator,

wherein all of the stated percentages are percentages by weight, basedupon total weight of (A), (B), (C) and (D); and

(c) a radiation-cured secondary coating layer comprising the curedreaction product of

(I) from about 40 percent to about 80 percent by weight of a mixture ofaliphatic urethane acrylate oligomers based on polyether backbones;

(II) from about 25 percent to about 50 percent by weight of a mixture ofisobornyl acrylate and hexanediol diacrylate; and

(III) from about 2.0 percent to about 7.0 percent by weight ofhydroxycyclohexylphenyl ketone photoinitiator; and

wherein all of the stated percentages are percentages by weight based onthe total weight of (I), (II) and (III).

The primary coating surrounding the fiber forms a cured polymericmaterial preferably having a glass transition temperature (Tg) of about-20° C. and preferably lower, i.e., about -30° C., or even lower.

The primary coating has an optimized adhesion to its substrate, highenough to remain adhered thereto under use conditions, yet not so highas to impair strippability for splicing. Preferably, the coating willrequire between about 10 and about 200 grams of force to peel it from aglass substrate at 50% relative humidity, and between about 5 and about100 grams of force at 95% relative humidity. It should be appreciated,however, that, in embodiments where stripping and splicing are limited,such as in transoceanic cables, even higher peel forces may beacceptable. It should also be appreciated that peel force is not aprecise, but rather a general, indicator of strippability from glassfibers.

When cured, the coating of the invention confers extraordinary thermal,hydrolytic and oxidative stability to the fiber and relieves stressthereon. Such long term stability is evidenced by acceptable performanceunder accelerated aging conditions of increased temperature andhumidity. Additionally, the coating has excellent resistance to bothwater and gasoline absorption, and the fiber so coated is otherwise wellprotected from environmental damage. Specifically, the coating exhibitsan increase in length from swelling (as a measure of solventpenetration) of no more than about 40% when soaked in gasoline at roomtemperature for four hours, and preferably no more than about 35%, and awater absorption value of no more than about 5% by weight, andpreferably no more than about 3% by weight, when tested in the mannerdescribed in Example I, infra.

The coating compositions of the present invention have been disclosedhereinabove for use as optical fiber coatings. However, it is to beunderstood that these coatings may be used in any embodiment whereinstable, water and solvent resistant coatings are desired, especially forcoating the surface of all optically useful article. For example, thecoatings may be used for such diverse end uses as coating sheet glass(i.e., in the preparation of safety glass) to coating vinyl materials(e.g., in preparing no-wax floors). Other optically useful articleswhich may be prepared include but are not limited to photoswitches,photorelay devices, microelectronic devices, photocoupling devices, andso forth.

EXAMPLES

The following Examples serve to further illustrate the invention. Inthese Examples and elsewhere throughout this application, all parts andpercentages are by weight, on a dry solids basis, and all temperaturesare in degrees centigrade unless expressly stated to be otherwise. Inall of the Examples, cure doses were measured with an InternationalLight IL 745-A radiometer with model A309 light bug. Unless otherwisenoted, throughout the Examples and the remainder of this application,"modulus" refers to 2.5% tensile modulus, measured using an Instrontensile tester. Unlike in the remainder of the application, wherepercentage by weight referred to the total weight of the (A) through (D)ingredients, parts by weight in the Examples refers to the totalcomposition described in that Example, including all components. Theoptional ingredients are identified by an asterisk (*) in the Examples.It should be noted that, although the specification teaches that thephotoinitiator is optional, it is required in the Examples, all of whichemploy ultraviolet cure. The other components are essential for use, ifthe exemplified coating is to meet the rigorous requirements for acommercially acceptable coating for optical glass fiber.

EXAMPLE I A Primary Coating Having Good Organic Solvent and WaterResistance Which is Thermally, Hydrolytically and Oxidatively Stable

The following composition was formulated:

    ______________________________________                                        Ingredient            Parts by Weight                                         ______________________________________                                        ALU-351 polyether-based                                                                             60.0                                                    aliphatic urethane acrylate                                                   oligomer based on polytetra-                                                  methylene polyol (from Echo                                                   Regins and Laboratory,                                                        Versailles, MO) (A)                                                           Aronix M-111 polyethylene glycol                                                                    approx. 21.00                                           nonylphenylether acrylate monomer                                             (from Toagasei Chemical Industry                                              Company Ltd., Tokyo, Japan) (B)                                               lauryl acrylate monomer (B)                                                                         4.20                                                    A-172 vinyl-tris-(2-methoxyethoxy                                                                   0.80                                                    silane) adhesion promoter (from                                               Union Carbide Corp., Danbury, CT.) (C)                                        Irgacure 184 hydroxycyclohexyl                                                                      6.00                                                    phenyl ketone photoinitiator (from                                            Ciba Geigy Corp., Hawthorne, NY.) (D)                                         Isooctyl 3-mercaptopropionate                                                                       7.00                                                    chain transfer agent (E)*                                                     Irganox 1035 thiodiethylene bis-                                                                    1.00                                                    (3,5-di-tert-butyl-4-hydroxy)                                                 hydrocinnamate antioxidant and                                                thermal stabilizer (from Ciba Geigy) (F)*                                     A-1110 3-aminopropyl trimethoxysilane                                                               0.00375                                                 shelf stabilizer (from Union Carbide) (F)*                                    ______________________________________                                    

The uncured coating composition had the following viscosity values atthese temperatures, measured by a Brookfield viscometer, model LVT, 6rpm, #34 spindle: 4250 cps at 25° C.; 3360 cps at 28° C.; 2810 cps at30° C.; 1940 cps at 35° C.; and 1305 cps at 40° C. The uncuredcomposition had a refractive index of 1.4870 at 24.2° C. and a densityof 8.66 lb/gal (1.04 g/cc).

A 6 mil coating of this composition was applied to a flat glass sheetusing a Bird applicator and cured in air at 0.7 J/cm² using a 200 wattsper inch medium pressure mercury vapor lamp.

Oxidative induction temperature was measured as follows. A sample of theabove coating was subjected to differential scanning calorimetry underoxygen at a flow rate of 20 cc/min. Approximately 10 milligram sampleswere heated in open pans by increasing the temperature at a rate of 10°C./minute from 100° C. to exotherm. The oxidative inductive temperature,or the point at which the exotherm began, was 200° C.

The cured film had a rupture strength of 91.1 psi; elongation at breakof 67.5%; TGA volatiles content of 6.53%; and a cured film refractiveindex of 1.4974 at 24.2° C. Its glass transition temperature, asmeasured by differential scanning calorimetry, was broad and indistinct.Its cure ratio (ratio of 2.5% moduli at 25° C. when cured in air at 0.2J/cm² and at 0.7 J/cm², respectively) was 79.7%.

The effect of temperature on 2.5% modulus of the cured film was asfollows: 25° C.:190.1 psi; 0° C.: 178.0 psi; -20° C.:403.7 psi; -40°C.:21,643.0 psi; and -60° C.:188,003.0 psi.

Water absorption of the sample was measured as follows. The cured filmwas equilibrated at 50% (±5%) relative humidity and 23° C. (±2° C.) for48 hours. After this conditioning, the sample was weighed and a weight"A" recorded. The sample was then soaked for 24 hours at 25° C. indistilled water, then patted dry and weighed; this weight was recordedas "B". The sample was next placed in a vacuum desiccator under 10 mmHgpressure at 25° C. for 24 hours, removed and again equilibrated at 50%(±5%) relative humidity and 23° C. (±2° C.) for 48 hours and weighed;this third weight was recorded as "C". Percent water absorption measuredas B-C/A×100 was about 1.78% for an average of three samples. This valueis referred to as the water absorption value.

Other samples of this 6 mil thick coating were tested as follows todetermine the effect of accelerated aging on various properties. Sampleswere conditioned for 48 hours at 50% (±5%) relative humidity and 25° C.(±2° C.). The samples were then placed on clips and hung in anenvironmental chamber under the following accelerated aging conditions:

(1) 125° C. for 7 days;

(2) 93.3° C. for 10 days;

(3) 93.3° C. for 10 days at 95% relative humidity (RH);

(4) 93.3° C. for 30 days; and

(5) 93.3° C. for 30 days at 95% relative humidity.

After the designated time period, the samples were removed andequilibrated at 23° C. (±2° C.) and 50% (±5%) relatively humidity for 48hours. The samples were then weighed and the following properties wererecorded:

    ______________________________________                                                              93.3° C. 93.3° C.                                125° C.                                                                      93.3° C.                                                                        10 days  93.3° C.                                                                      30 days                                        7 days                                                                              10 days  95% RH   30 days                                                                              95% RH                                  ______________________________________                                        weight   -7.16   -6.32    -1.98  -6.40  -2.63                                 change (%)                                                                    2.5% mod. at                                                                           192.2   204.8    194.3  203.0  145.8                                 25° C. (psi)                                                           2.5% modulus                                                                           -8.4%   -2.4%    -7.4%  -3.2%  -30.5%                                change (%)                                                                    at 25° C.                                                              rupture  98.6    109.6    88.0   97.2   71.4                                  strength (psi)                                                                % elongation                                                                           78.1    84.1     69.3   70.1   73.2                                  at break                                                                      ______________________________________                                    

Glass adhesion was measured using a normalized peel test in thefollowing manner. A 3 mil coating of this composition was applied to amicroscope slide and cured in air at 0.7 J/cm². A 3 mil coating of aliquid secondary coating was then applied atop this and cured in thesame manner. A one-inch slit was made down the center of the slide andthe slide conditioned at 23° C. (±2° C.) and 50% (±5%) relative humidityfor 24 hours and then put in the jaws of an Instron tensile tester,crosshead speed set at 20 mm/min, to measure peel force at 50% relativehumidity. For testing peel at 95% relative humidity, the slide wasconditioned for a further 24 hours at 95% (±5%) relative humidity andthen tested with the Instron as above. About 68 grams of force wererequired to peel the coating at 50% relative humidity and about 25 gramsat 95 % relative humidity.

Solvent resistance was measured by conducting a swell test wherein afilm sample was soaked in gasoline for four hours at room temperatureand length change measured. A percent change of 34.0 was noted.

EXAMPLE II Another Coating Having Excellent Organic Solvent and WaterResistance and Good Thermal, Hydrolytic and Oxidative Stability, ThoughSomewhat Poorer Strippability

A coating composition was made up as follows:

    ______________________________________                                        Ingredient            Parts by Weight                                         ______________________________________                                        ALU-351 polyether based                                                                             56.00                                                   aliphatic urethane acrylate                                                   oligomer based on polytetramethylene                                          polyol (from Echo Resins                                                      and Laboratory) (A)                                                           M-111 polyethylene glycol                                                                           29.99                                                   nonylphenylether acrylate                                                     monomer (from Toagasei Chemical                                               Industry Company) (B)                                                         A-172 vinyl-tris-(2-methoxyethoxy                                                                   1.00                                                    silane) adhesion promoter (from                                               Union Carbide) (C)                                                            Irgacure 184 hydroxycyclohexylphenyl                                                                6.00                                                    ketone photoinitiator (from Ciba                                              Geigy) (D)                                                                    Isooctyl 3-mercaptopropionate                                                                       6.00                                                    chain transfer agent (E)                                                      Irganox 1035 thiodiethylene                                                                         1.00                                                    bis-(3,5-di-tert-butyl-4-hydroxy)                                             hydrocinnamate antioxidant and                                                thermal stabilizer (from Ciba                                                 Geigy) (F)                                                                    A-1110 3-aminopropyl trimethoxysilane                                                               0.01                                                    shelf stabilizer (from Union Carbide) (F)                                     ______________________________________                                    

This coating composition, before cure, had the followingtemperature/viscosity profile, measured by a Brookfield viscometer,model LVT, 6 rpm, #34 spindle: 4720 cps at 25° C.; 3780 cps at 28° C.;3070 cps at 30° C.; 2060 cps at 35° C.; and 1385 cps at 40° C. Theliquid composition had a refractive index of 1.4908 at 25° C. and adensity of 8.58 lb/gal (1.03 g/cc).

A 6 mil coating of this composition was cast and cured as in Example I.

The cured film of this Example had a rupture strength of 82.6 psi;elongation at break of 57.4%; TGA volatiles content of 6.37%; oxidativeinduction temperature of 205° C.; and a cured film refractive index of1.5014 at 25° C. Its glass transition temperature was -31.7° C.(midpoint) (-35.8° C. onset) and its cure ratio (as described in ExampleI) was 85.9%.

The effect of temperature on 2.5% modulus was as follows for the curedfilm: 25° C.:226.0 psi; 0° C.: 217.0 psi; -20° C.:777.4 psi; -40°C.:71,796.0 psi; and -60° C.:222,675.0 psi.

An excellent value for water absorption of 1.40% was measured in themanner described in Example I, after a 24 hour soak, as an average ofthree samples.

Other samples of this coating were tested under the same acceleratedaging conditions as in Example I. The following properties were observedfor the cured coating described in this Example:

    ______________________________________                                                              93.3° C. 93.3° C.                                125° C.                                                                      93.3° C.                                                                        10 days  93.3° C.                                                                      30 days                                        7 days                                                                              10 days  95% RH   30 days                                                                              95% RH                                  ______________________________________                                        weight change                                                                           -6.89   -6.42    -0.89  -6.50  -0.23                                (%)                                                                           Tg (midpoint)                                                                           -29.4   -29.6    -32.8  -28.4  -33.9                                (°C.)                                                                  2.5% modulus                                                                            229.5   229.3    220.0  236.1  173.0                                at 25° C. (psi)                                                        2.5% modulus                                                                            6.8     6.7      2.4    9.9    -19.5                                change, % at                                                                  25° C.                                                                 rupture strength                                                                        126.1   137.6    93.4   117.2  90.7                                 (psi)                                                                         % elongation at                                                                         88.6    81.2     64.0   73.3   63.7                                 break                                                                         ______________________________________                                    

Glass adhesion, a measure of strippability, was measured at about 84grams of force at 50% relative humidity and about 28 grams at 95%relative humidity, considerably higher than the comparable values inExample I.

However, a percent change of only 31.2% was measured in the gasolineswell test, slightly superior to Example I.

EXAMPLE III A Primary Coating Having Organic Solvent and WaterResistance Which is Thermally, Hydrolytically and Oxidatively Stable

The following composition was made up:

    ______________________________________                                        Ingredient             Parts by Weight                                        ______________________________________                                        ALU-351 polyether-based                                                                              56.00                                                  aliphatic urethane acrylate                                                   oligomer based on polytetra-                                                  methylene polyol (from Echo                                                   Resins and Laboratory) (A)                                                    Aronix M-117 polypropylene                                                                           about 32.50                                            glycol nonylphenylether                                                       acrylate monomer (from Toagasei) (B)                                          A-172 vinyl-tris-(2-methoxyethoxy                                                                    1.00                                                   silane) adhesion promoter (from                                               Union Carbide) (C)                                                            Irgacure 184 hydroxycyclohexyl                                                                       4.00                                                   phenyl ketone photoinitiator                                                  (from Ciba-Geigy) (D)                                                         Isooctyl-3-mercaptopropionate                                                                        5.50                                                   chain transfer agent (E)*                                                     Irganox 1035 thiodiethylene                                                                          1.00                                                   bis-(3,5-di-tert-butyl-4-hydroxy)                                             hydrocinnamate antioxidant and                                                thermal stabilizer (from Ciba-                                                Geigy) (F)*                                                                   A-1110 3-aminopropyl   0.00375                                                trimethoxysilane shelf stabilizer                                             (from Union Carbide) (F)*                                                     ______________________________________                                    

Before cure, the coating composition of this Example had the followingtemperature/viscosity profile, measured by Brookfield viscometer, modelLVT, 6 rpm, #34 spindle: 25° C.:5440 cps; 28° C.:4280 cps; 30° C.:3490cps; 35° C.:2370 cps; and 40° C.:1085 cps. The uncured composition had arefractive index of 1.4852 at 26.0° C. and a density of 8.69 lb/gal(1.04 g/cc).

A 6 mil coating was cast and cured as in previous Examples.

The cured film of this Example had a rupture strength of 99.4 psi;elongation at break of 60.4%; TGA volatiles content of 4.86%; oxidativeinduction temperature of 193° C.; and a cured film refractive index of1.4949 at 25.7° C. Its glass transition temperature was -38.6° C.(midpoint) (-48.7° C. onset) and its cure ratio was 85.4%.

The effect of temperature on 2.5% modulus was as follows for the curedfilm: 25° C.:244.0 psi; 0° C.:223.8 psi; -20° C.:618 3 psi, -40°C.:49,187 psi; and -60° C.:202,582 psi.

A water absorption value, measured as in Example I, after a 24 hoursoak, of 1.58% was measured, as an average of three samples.

Other samples were subjected to the accelerated aging tests described inExample I, and the following properties observed:

    ______________________________________                                                              93.3° C. 93.3° C.                                125° C.                                                                      93.3° C.                                                                        10 days  93.3° C.                                                                      30 days                                        7 days                                                                              10 days  95% RH   30 days                                                                              95% RH                                  ______________________________________                                        weight   -6.07   -4.81    0.51   -5.26  -0.46                                 change (%)                                                                    2.5% modulus                                                                           238.5   253.9    234.0  259.4  199.3                                 at 25° C. (psi)                                                        2.5% modulus                                                                           -2.3%   4.1%     -4.1%  6.3%   -18.3%                                change (%)                                                                    at 25° C.                                                              rupture  92.5    100.9    94.1   95.2   84.2                                  strength (psi)                                                                % elongation                                                                           56.5    57.2     58.1   51.7   62.6                                  at break                                                                      ______________________________________                                    

The samples had excellent long term stability as well as organic solventand moisture resistance.

Glass adhesion was measured at about 31 grams of force at 50% relativehumidity and about 13 grams of force at 95% relative humidity, for anaverage of four samples. A percent change (length) of 34.7 was measuredafter a four hour soak in gasoline at room temperature.

EXAMPLE IV Another Primary Coating Having Acceptable Viscosity,Refractive Index and Strippability

The following coating composition was made up:

    ______________________________________                                        Ingredient          Parts by Weight                                           ______________________________________                                        ALU-352 polyether-based                                                                           55.0                                                      aliphatic urethane acrylate                                                   oligomer analogous to the                                                     oligomer of Example I except                                                  having a molecular weight about                                               1.5 times as high, a higher                                                   viscosity and a lower modulus                                                 (from Echo Resins) (A)                                                        Photomer 4003 polyethylene                                                                        22.0                                                      glycol nonylphenylether                                                       acrylate monomer (higher                                                      ethoxylation than M-111                                                       monomer used in Example                                                       I) (from Henkel Corporation,                                                  Ambler, PA) (B)                                                               lauryl acrylate monomer (B)                                                                       12.00                                                     A-172 vinyl-tris-(2-methoxy-                                                                      1.00                                                      ethoxy silane) adhesion promoter                                              (from Union Carbide) (C)                                                      Irgacure 184 hydroxycyclohexyl                                                                    6.00                                                      phenyl ketone photoinitiator (D)                                              Octadectyl-3-mercaptopropionate                                                                   2.50                                                      chain transfer agent (E)*                                                     Irganox 1035 thiodiethylene bis-                                                                  1.5                                                       (3,5-di-tert-butyl-4-hydroxy)                                                 hydrocinnamate antioxidant and                                                stabilizer (F)*                                                               ______________________________________                                    

This coating composition had a viscosity, at 25° C., of 4900 cps and arefractive index of 1.4795. A six mil film of this coating had desirablylow adhesion to a glass sheet. No accelerated aging tests wereperformed, but it is expected that the coating will perform well undersuch conditions.

EXAMPLE V A Composition Having Good Aging Characteristics But Less ThanOptimal Swelling

The following composition, similar to that of Example II, was made up:

    ______________________________________                                        Ingredient           Parts by Weight                                          ______________________________________                                        ALU-353 polyether-based                                                                            36.75                                                    aliphatic urethane acrylate                                                   oligomer analogous to the                                                     oligomer of Example II except                                                 having a molecular weight about                                               2.0 times that of ALU-351, a                                                  higher viscosity and a lower                                                  modulus (from Echo Resins) (A)                                                Aronix M-111 polyethylene glycol                                                                   55.00                                                    nonylphenylether acrylate                                                     monomer (from Toagasei) (B)                                                   A-172 vinyl-tris-(2-methoxyethoxy                                                                  1.00                                                     silane) (from Union Carbide) (C)                                              Irgacure 184 hydroxycyclohexyl                                                                     6.00                                                     phenyl ketone photoinitiator                                                  (from Ciba Geigy) (D)                                                         Isooctyl-3-mercaptopropionate                                                                      0.25                                                     chain transfer agent (E)*                                                     Irganox 1035 thiodiethylene bis-                                                                   1.00                                                     (3,5-di-tert-butyl-4-hydroxy)                                                 hydrocinnamate stabilizer (from                                               Ciba Geigy) (F)*                                                              ______________________________________                                    

The uncured coating had a viscosity of 5050 cps at 25° C. and a cureratio of 82.4%. The composition, when cast, cured and subjected to theaccelerated aging conditions of Example 1, performed well, but had aswelling value of 46.0%. This is believed to be a somewhat deleteriousresult of using a higher molecular weight oligomer.

EXAMPLE VI A Composition Exhibiting Low Swelling Prepared from A Mixtureof Oligomers and Absent A Chain Transfer Agent

The following composition was made:

    ______________________________________                                        Ingredient          Parts by Weight                                           ______________________________________                                        ALU-354 polyether-based                                                                           20.00                                                     aliphatic urethane acrylate                                                   oligomer analogous to that                                                    of Example I, but having a                                                    molecular weight about 2.6 times                                              as high (from Echo Resins) (A)                                                Uvithane ZL-1178 polyether-                                                                       20.00                                                     based aliphatic urethane                                                      acrylate oligomer (from Morton                                                Thiokol Inc., Princeton, NJ) (A)                                              Aronix M-111 polyethylene                                                                         52.00                                                     glycol nonylphenylether                                                       acrylate (from Toagasei) (B)                                                  A172 vinyl-tris-(2-methoxyethoxy                                                                  1.00                                                      silane) (from Union Carbide) (C)                                              Irgacure 184 hydroxy cyclohexyl-                                                                  6.00                                                      phenyl ketone photoinitiator                                                  from (Ciba Geigy) (D)                                                         Irganox 1035 thiodiethylene bis-                                                                  1.00                                                      (3,5-di-tert-butyl-4-hydroxy)                                                 hydrocinnamate stabilizer (from                                               Ciba Geigy) (F)*                                                              ______________________________________                                    

The composition had a viscosity of 6420 cps at 25° C. and a modulus of264.3 psi. When cast, cured and tested as in previous Examples, agasoline swelling measurement of 36.7% was recorded.

EXAMPLE VII A Composition Made From A Mixture of Oligomers

The following formulation was made up:

    ______________________________________                                        Ingredient           Parts by Weight                                          ______________________________________                                        ALU-350 polyether-based                                                                            36.00                                                    aliphatic urethane acrylate                                                   based on polytetramethylene                                                   polyol (from Echo Resins) (A)                                                 ALU-353 polyether acrylate                                                                         10.00                                                    analogous to ALU-350, but                                                     having 2.7 times the molecular                                                weight (Echo Resins) (A)                                                      Aronix M-111 polyethylene                                                                          35.00                                                    glycol nonylphenylether acrylate                                              (from Toagasei) (B)                                                           A-172 vinyl-tris-(2-methoxy-                                                                       2.00                                                     ethoxy silane) adhesion promoter                                              (from Union Carbide) (C)                                                      Irgacure 184 hydroxycyclohexyl-                                                                    6.00                                                     phenyl ketone photoinitiator (from                                            Ciba-Geigy) (D)                                                               Octadecyl-3-mercaptopropionate                                                                     10.00                                                    chain transfer agent (E)*                                                     Irganox 1035 thiodiethylene                                                                        1.00                                                     bis-(3,5-di-tert-butyl-4-hydroxy)                                             hydrocinnamate stabilizer (from                                               Ciba Geigy) (F)*                                                              A-1110 aminopropyl-3-methoxy-                                                                      0.01                                                     ethoxy silane (from Union                                                     Carbide) (F)*                                                                 ______________________________________                                    

This composition had a viscosity of 2620 cps at 25° C. When drawn downand cured as in earlier Examples, a cure ratio of 68.2%, a gasolineswelling value of 35.4%, and peel test values at 50% relative humidityof 105.0 grams and at 95% relative humidity of 45.4 grams were measured.

EXAMPLE VIII A Composition Having Good Solvent Resistance and GoodThermal Aging Properties

The following composition was made up:

    ______________________________________                                        Ingredient             Parts by Weight                                        ______________________________________                                        Purelast ® 569 polyether-based                                                                   8.0                                                    aliphatic urethane acrylate                                                   (from Polymer Systems Corp.,                                                  Orlando, Florida) (A)                                                         ALU-350 polyether-based                                                                              about 44.00                                            aliphatic urethane acrylate                                                   oligomer based on polytetra-                                                  methylene polyol (from Echo) (A)                                              Aronix M-111 polyethylene                                                                            34.00                                                  glycol nonylphenylether                                                       acrylate monomer (from Toagasei)                                              (B)                                                                           A-172 vinyl-tris-(2-methoxy-                                                                         2.00                                                   ethoxy silane) adhesion                                                       promoter (from Union Carbide) (C)                                             Irgacure 184 hydroxycyclohexyl-                                                                      6.00                                                   phenyl ketone photoinitiator                                                  (from Ciba Geigy) (D)                                                         Isooctyl-3-mercaptopropionate                                                                        5.00                                                   chain transfer agent (E)*                                                     Irganox 1035 thiodiethylene                                                                          1.00                                                   bis(3,5-di-tert-butyl-4-hydroxy)                                              hydrocinnamate stabilizer (from                                               Ciba Geigy) (F)*                                                              A-1110 3-aminopropyl   0.0025                                                 trimethoxysilane stabilizer (from                                             Union Carbide) (F)*                                                           ______________________________________                                    

The composition had a viscosity of 4100 cps at 25° C.

When cast and cured (at 0.7 J/cm² in air) as in preceding Examples, thecomposition performed well: it exhibited a 2.5% modulus at 25° C. of228.1 psi; swelled 28.4% in length after soaking in gasoline at roomtemperature for 4 hours; required 110 grams of force to peel at 50%relative humidity and 46 grams at 95% relative humidity; and performedwell after seven days' aging at 125° C.

EXAMPLE IX Another Composition Which Performed Well On Long Term ThermalAging

The following composition was made up:

    ______________________________________                                        Ingredient          Parts by Weight                                           ______________________________________                                        Purelast ® 566 polyether-                                                                     64.00                                                     based aliphatic urethane                                                      acrylate oligomer (from                                                       Polymer Systems Corp.) (A)                                                    Aronix M-117 polypropylene                                                                        20.00                                                     glycol nonylphenylether                                                       acrylate (from Toagasei) (B)                                                  lauryl acrylate (B) 10.00                                                     A-172 vinyl-tris (2-methoxy-                                                                      1.00                                                      ethoxy silane) adhesion promoter                                              (from Union Carbide) (C)                                                      Darocur 1173 hydroxymethyl-                                                                       4.00                                                      phenyl propanone photoinitiator                                               (from Ciba Geigy) (D)                                                         Irganox 1010 tetrakis [methylene                                                                  1.00                                                      (3,5-di-tert-butyl-4-hydroxy-                                                 hydrocinnamase)]methane                                                       ______________________________________                                    

This composition had a viscosity of 4920 cps at 25° C. It was cast andcured as in previous Examples, and, after cure, had a cure ratio of55.3%. It performed well after dry aging at 125° C. for 7 days.

EXAMPLE X A Composition Having Good Solvent Resistance and HigherAdhesion

The following composition was made up:

    ______________________________________                                        Ingredient             Parts by Weight                                        ______________________________________                                        Purelast ® 590 polyether-based                                                                   46.00                                                  aliphatic urethane acrylate                                                   oligomer (from Polymer Systems                                                Corp.) (A)                                                                    Aronix M-111 polyethylene                                                                            39.95                                                  glycol nonylphenylether                                                       acrylate monomer (from Toagasei) (B)                                          Lauryl acrylate (B)    5.00                                                   A-172 vinyl-tris-(2-methoxy-                                                                         1.00                                                   ethoxy silane) adhesion promoter                                              (from Union Carbide) (C)                                                      Irgacure 184 hydroxycyclohexyl-                                                                      4.00                                                   phenyl ketone photoinitiator (from                                            Ciba Geigy) (D)                                                               Isooctyl-3-mercaptopropionate chain                                                                  3.00                                                   transfer agent (E)*                                                           Irganox 1035 thiodiethylene                                                                          1.00                                                   bis (3,5-di-tert-butyl-4-hydroxy)                                             hydrocinnamate stabilizer (from                                               Ciba Geigy) (F)*                                                              A-1110 3-aminopropyl trimethoxysilane                                                                0.05                                                   stabilizer (F)                                                                ______________________________________                                    

The uncured composition had a viscosity of 4900 cps at 25° C.

When cast and cured as in previous Examples, the composition exhibited a2.5% modulus at 25° C. of 149.2 psi; swelled only 26.5% in length aftersoaking in gasoline at room temperature for 4 hours; and required 198.9grams of force to peel at 50% relative humidity. It is expected toperform well on long term aging.

EXAMPLE XI A Secondary Coating Formulation Suitable For Use With ThePrimary Coatings of this Invention

The following coating composition was prepared:

    ______________________________________                                        Ingredient             Parts by Weight                                        ______________________________________                                        Photomer 6008 aliphatic urethane                                                                     34.00                                                  acrylate oligomer with polyether                                              backbone, having an acrylate                                                  functionality of 2.6 (from Henkel                                             Corporation, Ambler, PA)                                                      AB2010A aliphatic urethane                                                                           34.00                                                  acrylate oligomer with                                                        polyether backbone, having an                                                 acrylate functionality                                                        of 2.4 (from American Biltrite                                                Inc., Lawrenceville, NJ)                                                      Hexanediol diacrylate  13.98                                                  Isobornyl acrylate     13.00                                                  Irgacure 184 hydroxycyclohexylphenyl                                                                 4.00                                                   ketone photoinitiator (from Ciba                                              Geigy)                                                                        Irganox 1035 thiodiethylene                                                                          1.00                                                   bis (3,5-di-tert-butyl-4-hydroxy)                                             hydrocinnamate stabilizer (from                                               Ciba Geigy)                                                                   DC 57 surface tension adjustment                                                                     0.02                                                   additive (from Dow Corning, Midland MI)                                       ______________________________________                                    

This coating composition, before cure, had the followingtemperature/viscosity profile, measured using a Brookfield viscometer,model LVT, 6 rpm, #34 spindle: 5430 cps at 25° C.; 4310 cps at 28° C.;3440 cps at 30° C.; 2310 cps at 35° C.; and 1520 cps at 40° C. Theliquid composition had a refractive index of 1.4856 at 24.6° C. and adensity of 8.89 lb/gal (1.07 g/cc).

A 6 mil coating of the composition was cast and cured as in previousExamples. The cured film of this Example had a rupture strength of 3812psi; elongation at break of 26.7%; TGA volatiles content of 4.78%;oxidative induction temperature of 210° C.; and cured film refractiveindex of 1.5060 at 24.6° C. Its cure speed was determined to be 0.4J/cm². The 2.5% tensile modulus of the coating was 90,528 psi at 25° C.and 4070 psi at 85° C. A water absorption value of 1.59% was measured inthe manner described in Example I, after a 24 hour soak.

Other samples of this coating were tested under the followingaccelerated aging conditions:

(1) 125° C. for 7 days;

(2) 93.3° C. for 10 days;

(3) 93.3° C. for 10 days at 95% RH;

(4) 93.3° C. for 30 days; and

(5) 93.3° C. for 30 days at 95% RH.

The following properties were observed for the cured coating describedin this Example:

    ______________________________________                                                              93.3° C. 93.3° C.                                125° C.                                                                      93.3° C.                                                                        10 days  93.3° C.                                                                      30 days                                        7 days                                                                              10 days  95% RH   30 days                                                                              95% RH                                  ______________________________________                                        weight   -4.42   -4.22    -0.88  -4.26  -2.42                                 change (%)                                                                    2.5% mod. at                                                                           124,633 122,136  88,281 122,522                                                                              97,850                                25° C. (psi)                                                           2.5% modulus                                                                           36.1    33.4     -3.6   33.8   6.9                                   change (%)                                                                    at 25° C.                                                              2.5% mod. at                                                                           4208    4343     3705   4408   3466                                  85° C. (psi)                                                           2.5% modulus                                                                           3.0     6.3      -9.3   7.9    -15.2                                 change (%)                                                                    at 85° C.                                                              rupture  4868    4362     3981   4535   3823                                  strength (psi)                                                                % elongation                                                                           30.7    25.8     30.0   30.3   21.8                                  at break                                                                      ______________________________________                                    

EXAMPLE XII Another Secondary Coating Formulation

The following coating composition was prepared:

    ______________________________________                                        Ingredient             Parts by Weight                                        ______________________________________                                        Photomer 6008 aliphatic                                                                              34.00                                                  urethane acrylate oligomer with                                               polyether backbone, having an                                                 acrylate functionality of 2.6                                                 (from Henkel Corporation)                                                     AB2010A aliphatic urethane                                                                           34.00                                                  acrylate oligomer with polyether                                              backbone, having an acrylate                                                  functionality of 2.4                                                          (from American Biltrite Inc.)                                                 Hexanediol diacrylate  13.99                                                  Isobornyl acrylate     13.00                                                  Irgacure 184 hydroxycyclohexylphenyl                                                                 4.00                                                   ketone photoinitiator (from Ciba                                              Geigy)                                                                        Irganox 1035 thiodiethylene                                                                          1.00                                                   bis (3,5-di-tert-butyl-4-hydroxy)                                             hydrocinnamate stabilizer                                                     (from Ciba Geigy)                                                             DC57 surface tension adjustment                                                                      0.01                                                   additive (from Dow Corning)                                                   ______________________________________                                    

The uncured coating of this Example had a refractive index of 1.4856 at24.2° C. and a viscosity of 5320 cps at 25° C.

A 6 mil coating was cast and cured as in previous Examples to produce acured film having an oxidative induction temperature of 194° C. and acure ratio (ratio of 2.5% moduli at 25° C. when cured in air at 0.2J/cm² and at 0.7 J/cm², respectively) of 100.9%.

The coating, which is very similar to that of the previous Example, isexpected to perform equally well on long term aging, and is similarlywell suited for use as a secondary coating atop the primary coatings ofthe invention.

Comparative Example I A Primary Coating Composition Which Aged Poorly

The following composition was formulated:

    ______________________________________                                        Ingredient           Parts by Weight                                          ______________________________________                                        CN-966 polyester-based                                                                             45.00                                                    aliphatic urethane acrylate                                                   oligomer (from Sartomer                                                       Company) (A)                                                                  Aronix M-111 polyethylene                                                                          34.50                                                    glycol nonylphenylether                                                       acrylate (from Toagasei Chemical                                              Industry Company, Ltd.) (B)                                                   lauryl acrylate (B)  11.00                                                    Chemlink-2000 50-50 mixture                                                                        1.50                                                     of linear C14 and C15 diol                                                    diacrylates (from Sartomer                                                    Company, Exton, PA) (B)                                                       A-172 vinyl-tris(2-methoxyethoxy                                                                   1.00                                                     silane) (from Union Carbide) (C)                                              Irgacure 184 hydroxycyclohexyl-                                                                    6.00                                                     phenyl ketone photoinitiator (D)                                              Irganox 1076 octadecyl-3,5-(di-tert-                                                               1.00                                                     butyl-4-hydroxy)hydrocinnamate                                                stabilizer (from Ciba Geigy) (F)*                                             ______________________________________                                    

The liquid coating had an acceptable viscosity of 4630 cps at 25° C.,and a good cure ratio of 62.4%, but, when cast on a glass sheet as a 6mil coating, cured, and subjected to the accelerated aging testsdescribed in Example I, performed very poorly under high humidity and/orhigh temperature conditions.

Comparative Example II A Composition Having Good Solvent Resistance ButPoor Thermal Aging Stability

A composition was made up which was identical to that of Example VIIIabove, but containing, in lieu of the Purelast® 569 oligomer, Purelast®169V oligomer, an analogous oligomer to 569 but based on an aromaticpolyether rather than on an aliphatic polyether and of higher molecularweight.

This composition had a viscosity of 4230 cps at 25° C., and performedwell, before thermal aging, as well: it had a 2.5% modulus of 214.1 psi(when cured in air at 0.7 J/cm²); swelled 28.2% when soaked in gasoline;and required 85.0 grams and 39.6 grams of force at 50% and 95% relativehumidity, respectively, to peel. However, upon thermal aging at 125° C.for only 3 days, an exudate was noted, indicating thermal instability.

CONCLUSION

The primary coatings of the present invention, then, have severalimportant qualities which make optical fibers coated with them usefulfor many applications and particularly suitable in local area networksfor fiber-to-the-home uses.

These coatings, when cured, possess excellent thermal, hydrolytic andoxidative stability over the long term, as predicted by acceleratedaging tests at increased temperature and humidity, and are resistant topenetration of both water and organic solvents in order to protect theintegrity of the underlying fibers.

While the invention has been disclosed in this patent application byreference to the details of preferred embodiments of the invention, itis to be understood that this disclosure is intended in an illustrativerather than in a limiting sense, as it is contemplated thatmodifications will readily occur to those skilled in the art, within thespirit of the invention and the scope of the appended claims.

What is claimed is:
 1. A radiation-curable primary coating compositionfor an optical fiber comprising(A) from about 10 percent to about 90percent by weight of an acrylate or methacrylate terminated urethaneoligomer said oligomer having a number average molecular weight of notmore than about 4,430 daltons which consists essentially of only carbon,hydrogen, nitrogen and oxygen atoms and which is the reaction product of(i) a polyether polyol; (ii) a non-aromatic polyisocyanate; and (iii) anendcapping monomer capable of providing an acrylate or methacrylateterminus; (B) from about 5 percent to about 80 percent by weight of oneor more monomer diluents which do not adversely affect the compositionwhen cured and which are selected from the group consisting of(i) alkylacrylate and methacrylate monomers having 6 to 18 carbon atoms in thealkyl moiety; (ii) monomers having (1) an aromatic moiety, (2) a moietycontaining acrylic or methacrylic unsaturation, and (3) a hydrocarbonmoiety, which monomer (ii) is capable of increasing the refractive indexof the composition relative to that of a composition containing only(A), (C) and (D), and (iii) mixtures thereof; (C) from about 0.1 percentto about 3.0 percent by weight of an organofunctional silane adhesionpromoter which binds in with the coating composition during cure; and(D) optionally, from about 1.0 percent to about 10.0 percent by weightof a photoinitiator, wherein all of the stated percentages arepercentages by weight based on total weight of (A), (B), (C) and (D),wherein the composition, after radiation cure, remains adherent andexhibits thermal, hydrolytic and oxidative stability at temperatures inexcess of 90° C. and at 95% relative humidity and an increase in lengthfrom swelling of no more than about 40 percent when soaked in gasolinefor four hours at room temperature and a water absorption value of nomore than about 5% by weight; wherein the composition is devoid ofacid-functional materials; and wherein said primary coating composition,after radiation cure, has a tensile modulus of less than 500 psi.
 2. Aradiation-curable coating composition according to claim 1 wherein saidpolyether polyol (i) is based on a straight chained or branched alkyleneoxide of from one to about twelve carbon atoms.
 3. A radiation-curableprimary coating composition for an optical fiber according to claim 1wherein said non-aromatic polyisocyanate (ii) is selected from the groupconsisting of isophorone diisocyanate;dicyclohexylmethane-4,4'-diisocyanate; 1,6-hexamethylene diisocyanate;trimethylhexamethylene diisocyanate; and mixture thereof.
 4. Aradiation-curable coating composition according to claim 1 wherein saidmonomer (B) is selected from the group consisting of hexyl acrylate;hexyl methacrylate; 2-ethylhexyl acrylate; 2-ethylhexyl methacrylate;isooctyl acrylate; isooctyl methacrylate; octyl acrylate; octylmethacrylate; decyl acrylate; decyl methacrylate; isodecyl acrylate;isodecyl methacrylate; lauryl acrylate; lauryl methacrylate; tridecylacrylate; tridecyl methacrylate; palmitic acrylate; palmiticmethacrylate; stearyl acrylate; stearyl methacrylate; C₁₄ -C₁₅hydrocarbon diol diacrylates; C₁₄ -C₁₅ hydrocarbon diol diacrylates;polyalkylene glycol nonylphenylether acrylates; polyalkylene glycolnonylphenylether methacrylates; and mixtures thereof.
 5. Aradiation-curable coating composition according to claim 1 wherein saidmonomer component (B) comprises a mixture of(i) a monomer selected fromthe group consisting of lauryl acrylate; stearyl acrylate; isodecylacrylate; and mixtures thereof, and (ii) a monomer selected from thegroup consisting of polyethylene glycol nonylphenylether acrylate;polypropylene glycol nonylphenylether acrylate; and mixtures thereof. 6.A radiation-curable coating composition according to claim 1 whereinsaid silane adhesion promoter (C) is selected from the group consistingof amino-functional silanes; mercapto-functional silanes;methacrylate-functional silanes; acrylamido-functional silanes;allyl-functional silanes; vinyl-functional silanes; acrylate-functionalsilanes; and mixtures thereof.
 7. A radiation-curable coatingcomposition according to claim 1 wherein said silane adhesion promoter(C) is selected from the group consisting of mercaptoalkyl trialkoxysilane; vinyl alkoxy silane; methacryloxyalkyltrialkoxy silane;aminoalkyl trialkoxy silane; and mixtures thereof.
 8. Aradiation-curable coating composition according to claim wherein saidsilane adhesion promoter (C) is vinyl-tris- (2-methoxyethoxy silane). 9.A radiation-curable coating composition according to claim 1 whereinsaid photoinitiator (D) is selected from the group consisting ofhydroxycyclohexylphenyl ketone; hydroxymethylphenyl propanone;dimethoxyphenyl acetophenone; 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propanone-1;1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one;1-(4-dodecylphenyl)-2-hydroxy-2-methylpropan-1-one;4-(2-hydroxyethoxy)phenyl-2-(2-hydroxy-2-propyl)ketone;diethoxyacetophenone; 2,2-di-sec-butoxyacetophenone; diethoxyphenylacetophenone; and mixtures thereof.
 10. A radiation-curable coatingcomposition according to claim 1 wherein said photoinitiator (D) ishydroxycyclohexylphenyl ketone.
 11. A radiation-curable coatingcomposition according to claim 1 additionally comprising from about 0.1percent to about 10 percent by weight, based on total weight of (A),(B), (C) and (D), of a mercapto functional chain transfer agent (E). 12.A radiation-curable coating composition according to claim 11 whereinsaid chain transfer agent (E) is selected from the group consisting ofmethyl thioglycolate; methyl-3-mercaptopropionate; ethyl thioglycolate;butyl thioglycolate; butyl-3-mercaptopropionate; isooctyl thioglycolate;isooctyl-3-mercaptopropionate; isodecyl thioglycolate;isodecyl-3-mercaptopropionate; dodecyl thioglycolate;dodecyl-3-mercaptopropionate; octadecyl thioglycolate;octadecyl-3-mercaptopropionate; and mixtures thereof.
 13. Aradiation-curable coating composition according to claim 11 wherein saidchain transfer agent is isooctyl-3-mercaptopropionate.
 14. Aradiation-curable coating composition to claim 1 additionally comprisingfrom about 0.0001 percent to about 3.0 percent by weight, based on totalweight of (A), (B), (C) and (D), of a stabilizer (F) selected from thegroup consisting of organic phosphites; silanes; hindered phenols;amines; and mixtures thereof.
 15. A radiation-curable coatingcomposition according to claim 14 wherein said stabilizer (F) is3-aminopropyl trimethoxysilane.
 16. A radiation-curable coatingcomposition according to claim 14 wherein said stabilizer (F) isthiodiethylene bis-(3,5-di-tert-butyl-4-hydroxy) hydrocinnamate.
 17. Aradiation-curable primary coating composition for an optical fibercomprising(A) from about 10 percent to about 90 percent by weight of anacrylate- or methacrylate-terminated urethane oligomer said oligomerhaving a number average molecular weight of not more than about 2,300daltons which consists essentially of only carbon, hydrogen, nitrogenand oxygen atoms and which is the reaction product of (i) a polyetherpolyol; (ii) a non-aromatic polyisocyanate; and (iii) an endcappingmonomer selected from the group consisting of hydroxyalkylacrylate andhydroxyalkylmethacrylate; (B) from about 5 percent to about 80 percentby weight of one or more acrylate or methacrylate monomer diluents andwhich do not adversely affect the composition when cured and which areselected from the group consisting of(i) alkyl acrylate and methacrylatemonomers having 6 to 18 carbon atoms in the alkyl moiety; (ii) monomershaving (1) an aromatic moiety, (2) a moiety containing acrylic ormethacrylic unsaturation, and (3) a hydrocarbon moiety, which monomer(ii) is capable of increasing the refractive index of the compositionrelative to that of a composition containing only (A), (C) and (D), and(iii) and mixtures thereof; (C) from about 0.1 percent to about 3.0percent by weight of an organofunctional silane adhesion promoter whichbinds in with the coating composition during cure; and (D) optionally,from about 1.0 percent to about 10 percent by weight of aphotoinitiator, wherein all of the stated percentages are percentages byweight based on total weight of (A), (B), (C) and (D) wherein thecomposition, after radiation cure, remains adherent and exhibitsthermal, hydrolytic and oxidative stability at temperatures in excess of90° C. and at 95% relative humidity and an increase in length fromswelling of no more than about 30 percent when soaked in gasoline forfour hours at room temperature and a water absorption value of no morethan about 5% by weight; wherein the composition is devoid ofacid-functional materials; and wherein said primary coating composition,after radiation cure, has a tensile modulus of less than 500 psi.
 18. Aradiation-curable coating composition according to claim 17 wherein saidpolyether polyol (i) is based on a straight chained or branched alkyleneoxide of from one to about twelve carbon atoms.
 19. A radiation-curableprimary coating composition according to claim 17 wherein said aliphaticpolyisocyanate (ii) is selected from the group consisting of isophoronediisocyanate; dicyclohexylmethane-4,4'-diisocyanate; 1,6-hexamethylenediisocyanate; trimethylhexamethylene diisocyanate; and mixture thereof.20. A radiation-curable coating composition according to claim 17wherein said monomer (B) is selected from the group consisting of hexylacrylate; hexyl methacrylate; 2-ethylhexyl acrylate; 2-ethylhexylmethacrylate; isooctyl acrylate; isooctyl methacrylate; octyl acrylate;octyl methacrylate; decyl acrylate; decyl methacrylate; isodecylacrylate; isodecyl methacrylate; lauryl acrylate; lauryl methacrylate;tridecyl acrylate; tridecyl methacrylate; stearyl acrylate; stearylmethacrylate; C₁₄ -C₁₅ hydrocarbon diol diacrylates; C₁₄ -C₁₅hydrocarbon diol dimethacrylates; polyalkylene glycol nonylphenyletheracrylates; polyalkylene glycol nonylphenylether methacrylates; andmixtures thereof.
 21. A radiation-curable coating composition accordingto claim 17 wherein said monomer component (B) comprises a mixture of(i)a monomer selected from the group consisting of lauryl acrylate; stearylacrylate; isodecyl acrylate; and mixtures thereof, and (ii) a monomerselected from the group consisting of polyethylene glycolnonylphenylether acrylate; polypropylene glycol nonylphenyletheracrylate; and mixtures thereof.
 22. A radiation-curable coatingcomposition according to claim 17 wherein said silane adhesion promoter(C) is selected from the group consisting of amino-functional silanes;mercapto-functional silanes; methacrylate-functional silanes;acrylamido-functional silanes; allyl-functional silanes;vinyl-functional silanes; acrylate-functional silanes; and mixturesthereof.
 23. A radiation-curable coating composition according to claim17 wherein said silane adhesion promoter (C) is selected from the groupconsisting of mercaptoalkyl trialkoxy silane; vinyl alkoxy silane;methacryloxyalkyltrialkoxy silane; aminoalkyl trialkoxy silane; andmixtures thereof.
 24. A radiation-curable coating composition accordingto claim 17 wherein said silane adhesion promoter (C) is vinyl-tris-(2-methoxyethoxy silane).
 25. A radiation-curable coating compositionaccording to claim 17 wherein said photoinitiator (D) is selected fromthe group consisting of hydroxycyclohexylphenyl ketone;hydroxymethylphenyl propanone; dimethoxyphenyl acetophenone;2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propanone-1;1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one;1-(4-dodecylphenyl)-2-hydroxy-2-methylpropan-1-one;4-(2-hydroxyethoxy)phenyl-2(2-hydroxy-2-propyl)ketone;diethoxyacetophenone; 2,2-di-sec-butoxyacetophenone; diethoxyphenylacetophenone; and mixtures thereof.
 26. A radiation-curable coatingcomposition according to claim 17 wherein said photoinitiator (D) ishydroxycyclohexylphenyl ketone.
 27. A radiation-curable coatingcomposition according to claim 17 additionally comprising from about 0.1percent to about 10 percent by weight, based on total weight of (A),(B), (C) and (D), of a mercapto functional chain transfer agent (E). 28.A radiation-curable coating composition according to claim 27 whereinsaid chain transfer agent (E) is selected from the group consisting ofmethyl thioglycolate; methyl-3-mercaptopropionate; ethyl thioglycolate;butyl thioglycolate; butyl-3-mercaptopropionate; isooctyl thioglycolate;isooctyl-3-mercaptopropionate; isodecyl thioglycolate;isodecyl-3-mercaptopropionate; dodecyl thioglycolate;dodecyl-3-mercaptopropionate; octadecyl thioglycolate;octadecyl-3-mercaptopropionate; and mixtures thereof.
 29. Aradiation-curable coating composition according to claim 27 wherein saidchain transfer agent is isooctyl-3-mercaptopropionate.
 30. Aradiation-curable coating composition according to claim 17 additionallycomprising from about 0.0001 percent to about 3.0 percent by weight,based on total weight of (A), (B), (C) and (D), of a stabilizer (F)selected from the group consisting of organic phosphites; silanes;hindered phenols; amines; and mixtures thereof.
 31. A radiation-curablecoating composition according to claim 30 wherein said stabilizer (F) is3-aminopropyl trimethoxysilane.
 32. A radiation-curable coatingcomposition according to claim 30 wherein said stabilizer (F) isthiodiethylene bis-(3,5-di-tert-butyl-4-hydroxy) hydrocinnamate.
 33. Aradiation-curable primary coating composition for an optical fiber,comprising(A) from about 30 percent to about 70 percent by weight of anon-aromatic urethane acrylate oligomer said oligomer having a numberaverage molecular weight of not more than about 4,430 daltons whichconsists essentially of only carbon, hydrogen, nitrogen and oxygen atomsand having as a backbone polytetramethylene polyol; (B) from about 10percent to about 60 percent by weight of a mixture of (i) polyethyleneglycol nonylphenylether acrylate and (ii) lauryl acrylate; (C) fromabout 0.3 percent to about 1.0 percent by weight ofvinyl-tris-(2-methoxyethoxy silane) adhesion promoter which binds inwith the coating composition during cure; and (D) from about 2.0 percentto about 7.0 percent by weight of hydroxycyclohexylphenyl ketonephotoinitiator, wherein all of the stated percentages are percentages byweight, based on total weight of (A), (B), (C) and (D), wherein thecomposition, after radiation cure, remains adherent and exhibitsthermal, hydrolytic and oxidative stability at temperatures in excess of90° C. and at 95% relative humidity and an increase in length fromswelling of no more than about 40 percent when soaked in gasoline forfour hours at room temperature and a water absorption value of no morethan about 5% by weight; wherein the composition is devoid ofacid-functional materials; and wherein said primary coating composition,after radiation cure, has a tensile modulus of less than 500 psi.
 34. Aradiation-curable coating composition according to claim 33 additionallycomprising from about 0.5 percent to about 8.0 percent by weight, basedon total weight of (A), (B), (C) and (D), ofisooctyl-3-mercaptopropionate.
 35. A radiation-curable coatingcomposition according to claim 33 additionally comprising from about 0.5percent to about 1.5 percent by weight, based on total weight of (A),(B), (C) and (D), of thiodiethylene bis-(3,5-di-tert-butyl-4-hydroxy)hydrocinnamate.
 36. A radiation-curable coating composition according toclaim 33 additionally comprising from about 0.0001 percent to about 0.01percent by weight of 3-aminopropyl trimethoxysilane.
 37. Aradiation-curable primary coating composition for an optical fiber,comprising(A) from about 30 percent to about 70 percent by weight of anon-aromatic urethane acrylate oligomer said oligomer having a numberaverage molecular weight of not more than about 4,430 daltons whichconsists essentially of only carbon, hydrogen, nitrogen and oxygen atomsand having as a backbone polytetramethylene polyol; (B) from about 10percent to about 60 percent by weight of polyethylene glycolnonylphenylether acrylate; (C) from about 0.3 percent to about 1.0percent by weight of vinyl-tris-(2-methoxyethoxy silane) adhesionpromoter which binds in with the coating composition during cure; and(D) from about 2.0 percent to about 7.0 percent by weight ofhydroxycyclohexylphenyl ketone photoinitiator, wherein all of the statedpercentages are percentages by weight, based on total weight of (A),(B), (C) and (D), wherein the composition, after radiation cure, remainsadhered and exhibits thermal, hydrolytic and oxidative stability attemperatures in excess of 90° C. and at 95% relative humidity and anincrease in length from swelling of no more than about 40 percent whensoaked in gasoline for four hours at room temperature and a waterabsorption value of no more than about 5% by weight; wherein thecomposition is devoid of acid-functional materials; and wherein saidprimary coating composition, after radiation cure, has a tensile modulusof less than 500 psi.
 38. A radiation-curable coating compositionaccording to claim 37 additionally comprising from about 0.5 percent toabout 8.0 percent by weight, based on total weight of (A), (B), (C) and(D), of isooctyl-3-mercaptopropionate.
 39. A radiation-curable coatingcomposition according to claim 37 additionally comprising from about 0.5percent to about 1.5 percent by weight, based on total weight of (A),(B), (C) and (D), of thiodiethylene bis-(3,5-di-tert-butyl-4-hydroxy)hydrocinnamate.
 40. A radiation-curable coating composition according toclaim 37 additionally comprising from about 0.0001 percent to about 0.01percent by weight of 3-aminopropyl trimethoxysilane.
 41. Aradiation-curable primary coating composition for an optical fiberconsisting essentially of(A) from about 10 percent to about 90 percentby weight of a reactively terminated urethane oligomer said oligomerhaving a number average molecular weight of not more than about 4,430daltons which consists essentially of only carbon, hydrogen, nitrogenand oxygen atoms and which is the reaction product of (i) a polyetherpolyol; (ii) non-aromatic polyisocyanate; and (iii) an endcappingmonomer capable of providing an acrylate or methacrylate terminus; (B)from about 5 percent to about 80 percent by weight of one or moremonomers having (1) an aromatic moiety, (2) a moiety containing acrylicor methacrylic unsaturation, and (3) a hydrocarbon moiety, which monomer(B) is capable of increasing the refractive index of the compositionrelative to that of a composition containing only (A), (C) and (D); (C)from about 0.1 percent to about 3.0 percent by weight of anorganofunctional silane adhesion promoter which binds in with thecoating composition during cure; and (D) optionally, from about 1.0percent to about 10.0 percent by weight of a photoinitiator, wherein allof the stated percentages are percentages by weight based on totalweight of (A), (B), (C) and (D), wherein the composition, afterradiation cure, exhibits thermal, hydrolytic and oxidative stabilityincluding adequate adhesion at temperatures in excess of 90° C. and at95% relative humidity and an increase in length from swelling of no morethan about 40 percent when soaked in gasoline for four hours at roomtemperature and a water absorption value of no more than about 5% byweight; wherein the composition is devoid of acid-functional materials;and wherein said coating composition, after radiation cure, has atensile modulus of less than 500 psi.
 42. A radiation-curable primarycoatingcomposition for optical fiber according to claim 41 additionallycomprising from about 0.1 percent to about 10 percent by weight based ontotal weight of (A), (B), (C) and (D), of a mercapto functional chaintransfer agent (E).
 43. A radiation-curable primary coating compositionfor an optical fiber according to claim 41 additionally comprising fromabout 0.0001 percent to about 3.0 percent by weight, based on totalweight of (A) (B), (C) and (D), of a stabilizer (F) selected from thegroup consisting of organic phosphites; silanes; hindered phenols;amines; and mixtures thereof.